1. Field of the Invention
The invention relates to a hard-metal or ceramic drill blank with at least one helically extending internal flushing bore, and to a method for producing the blank roughly comprising heating the hard-metal or ceramic material to its extrusion temperature, pressing the heated material through a space defined by a mandrel and a nozzle to helically twist the blank. This invention also relates to an extrusion tool for manufacturing the drill blank of the invention.
2. Description of the Prior Art
Extrusion processes and hard-metal or sintered drill blanks are known, e.g., from European patent application No. 0,118,035 Al. The blanks produced by means of helical twisting as described in this patent application still need to have chip spaces ground out. This involves not only a separate step but also considerable costs. To produce the hard-metal drill tip, this patent application proposes that a circular-cylindrical sintered metal blank be extruded by means of an extrusion device having an extrusion die nozzle.
The helically extending cooling conduits are then produced by twisting of the sintered metal blank emerging from the extrusion device with an angular speed adapted to the flow of material, the desired drill geometry and the helical course of the cooling conduits. The twisting devices provide a steady and uniform axial guidance of the sintered metal blank and an equally continuous and steady twisting movement.
Accordingly, the prior art method has the disadvantage of requiring not only an extrusion tool but also additional twisting devices and corresponding control and regulating devices.